Random Homozygous Knockout (RHK) technology is a method of reversibly inserting promoters downstream of transcriptionally active genes, in the antisense orientation. The antisense RNA transcribed from these promoters downregulates expression of RNA from both alleles of a modified gene, achieving homozygous "knockout." Selecting a library of such RHK insertions, selects cells with desired characteristics conferred upon them by inactivation of individual cellular genes. These genes can then be cloned and identified by their proximity to the inserted promoter. Technical considerations peculiar to retroviruses in general and to HIV in particular,lead me to propose selecting for cellular genes that are dispensable for cellular growth and replication, but which are critical for post-integration HIV expression. Such genes should be valuable therapeutic targets.